1. Field of the Invention
The invention pertains to the art of vehicle controls and more particularly to controls for skid-steered tractor vehicles having separate hydrostatic transmissions. A four-wheel skid-steered vehicle of the type to which the present invention pertains is disclosed in U.S. Pat. No. 3,635,365 entitled "Tractor Vehicle With Hydrostatic Drive Means", issued Jan. 18, 1972 to the inventor, James J. Bauer, and assigned to the assignee of the present invention.
2. Description of the Prior Art
Skid-steered loader vehicles of the type disclosed in the aforementioned patent will have right and left hydrostatic transmissions independently controlled by a pair of steering levers, one for each transmission, movable forward or back to vary the speed and power output of the transmissions in either forward or reverse directions.
A centering mechanism is used to return the levers to the neutral position once released by the operator. Such a centering mechanism is disclosed in U.S. Pat. No. 3,605,519 entitled "Control for Dual Hydrostatic Drive", issued Sept. 20, 1971, to the inventor, John P. Heggen, and assigned to the assignee of the present invention.
The centering mechanism of U.S. Pat. No. 3,605,519 is mounted at one end of the control shaft, on which the steering levers pivot and generally takes the form of a roller which travels in a V-shaped cam leaf biased by a spring such that when the levers are released, the roller is urged to the lowest point in the cam leaf which coincides with the neutral position of the levers.
The loader or material handling portions of the vehicle will be oprated by a pair of hydraulic cylinders to raise and lower the boom arms and to tilt or roll back the attachment carrier mounting an attachment such as a bucket. A control valve having separate valve sections operates the hydraulic cylinders. The separate sections are individually actuated by a linkage controlled by foot pedals in the operator's compartment.